JP2002260248A - Mirror detection signal generation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an amplitude variation detection circuit which can stably detect a mirror part, independent of the kind of an optical recording medium, and an information reproducing apparatus having the same. SOLUTION: A top envelope signal Ste of an RF (radio frequency) signal Srf and a bottom hold signal Sbh, of which the voltages are divided by a voltage dividing circuit 16, are added to a prescribed offset at an offset circuit 22 after being amplified by a gain control amplifier 19 with the gain according to the kind of an optical disk 1, and inputted to a comparator 24, as a mirror detection threshold signal Smt. A bottom envelope signal Sbe of the RF signal Srf, of which the high-frequency noise component is removed by a low-pass filter 21, is inputted to the comparator 24 after being amplified by a gain control amplifier 20 with the gain according to the kind of the optical disk 1. A mirror detection signal Sm is generated according to the comparison result of the level of the amplified bottom envelope signal S4 with that of the mirror detection threshold signal Smt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mirror detection signal generating circuit for detecting a mirror portion of an optical recording medium from fluctuations in the amplitude of an RF signal read by an optical pickup during reproduction of the optical recording medium.

[0002]

2. Description of the Related Art CD (Compact Disc) and DVD (Digita
l On a disk-type optical recording medium (hereinafter, referred to as an optical disk) such as a versatile disk, an elongated convex portion called a pit having a length corresponding to recording data is formed on a recording surface of the disk irradiated with laser light. Many are formed. The pits are arranged in a spiral form in a row from the center of the recording surface to the outer periphery in accordance with the recording order of data, and when recording data is read from the optical disk, the pit row is irradiated with laser light. . The intensity of the reflected light of the irradiated laser becomes weak when the spot of the laser light is on the pit, and becomes strong when it is on a flat surface portion other than the pit. The information recorded on the optical disk is electrically reproduced by converting the intensity of the reflected light into an electric signal by a photodetector such as a photodiode. The electric signal output from the photodetector in accordance with the intensity of the reflected light is also called an RF signal because it is modulated at a high frequency in accordance with the presence or absence of a pit.

[0003] Further, one round of the spirally arranged pit row is called a track, and an optical disk reproducing apparatus such as a CD or DVD has a function of reproducing recorded data by skipping this track. I have. One of the characteristics of the disk-type optical recording medium is that the skip reproduction is faster than the tape-type recording medium.

In order to reproduce information recorded at a desired position on an optical disk by jumping over a track, it is necessary to determine on which track the laser beam spot is currently located and from which track the jump destination track is located. Need to figure out. A general optical disc reproducing apparatus includes a circuit called a mirror detection circuit that detects whether a light spot is on a track or a flat mirror portion other than the track. By counting the number of track portions and mirror portions that are alternately detected by the mirror detection circuit when crossing, the number of tracks that have moved can be ascertained.

[0005]

FIG. 5 is a schematic block diagram showing a configuration example of a conventional mirror detection circuit and a conventional defect detection circuit. Mirror detection circuit 200a shown in FIG.
Are the peak hold circuit 102 to the peak hold circuit 1
04, a voltage dividing circuit 106, an offset circuit 107 and a comparator 109. The defect detection circuit 200b shown in FIG. 5 includes a peak hold circuit 101, a voltage division circuit 105, and a comparator 108, and shares the peak hold circuit 102 and the peak hold circuit 103 with the mirror detection circuit 200a.

The peak hold circuit 101 to the peak hold circuit 104 form a maximum peak level (hereinafter referred to as a top level) or a minimum peak level (hereinafter referred to as a bottom level) of the RF signal Srf converted into an electric signal in the photodetector. ). The peak hold circuit 101 and the peak hold circuit 102 hold the top level of the RF signal Srf,
03 and the peak hold circuit 104 hold the bottom level of the RF signal Srf.

A droop rate, which indicates a rate at which the holding level of the peak hold circuit attenuates with time, is set individually for each peak hold circuit. The nature of the signal held in the circuit is different. The peak hold circuit 101 is set with a relatively slow droop rate to output a top hold signal Sth in which the top level of the RF signal Srf is held constant. For example, a droop rate of about 1 [msec / V] is set. The peak hold circuit 102 has a droop rate faster than that of the peak hold circuit 101 in order to output a top envelope signal Ste according to an envelope drawn by the top level of the RF signal Srf. For example, a droop rate of about 100 [usec / V] is set. The peak hold circuit 103 is set to have a relatively slow droop rate in order to output the bottom hold signal Sbh in which the bottom level of the RF signal Srf is kept constant. For example, a droop rate of about 10 [msec / V] is set. The peak hold circuit 104
In order to output a bottom envelope signal Sbe corresponding to an envelope drawn by the bottom level of the F signal Srf, a droop rate faster than the peak hold circuit 102 or the peak hold circuit 103 is set. For example, 10 [use
c / V].

The voltage dividing circuit 105 includes a peak hold circuit 1
01 top hold signal Sth and peak hold circuit 1
A defect detection threshold signal Sdt obtained by dividing the voltage of the bottom hold signal Sbh of FIG. 03 by a predetermined ratio is input to the positive terminal of the comparator 108. The voltage dividing circuit 106 inputs a signal obtained by dividing the top envelope signal Ste of the peak hold circuit 102 and the bottom hold signal Sbh of the peak hold circuit 103 at a predetermined ratio to the offset circuit 107. The offset circuit 107 adds a predetermined offset to the divided voltage signal output from the voltage dividing circuit 106, and inputs this to the negative terminal of the comparator 109 as a mirror detection threshold signal Smt.

Comparator 108 and Comparator 1
09 compares the signal level input to the positive terminal with the signal level input to the negative terminal. If the signal level of the positive terminal is higher than that of the negative terminal, a logical value '09
It outputs a signal of 1 'and outputs a logical value of' 0 'if smaller. When the top envelope signal Ste becomes smaller than the above-described defect detection threshold signal Smd, the comparator 108 outputs a defect detection signal Sd having a logical value “1” for notifying the detection of a defect on the optical disk. When the bottom envelope signal Sbe is larger than the above-described mirror detection threshold signal Smt, the comparator 109 outputs a mirror detection signal Sm having a logical value “1” notifying the detection of the mirror portion.

Next, the operation of the mirror detection circuit 200a and the defect detection circuit 200b having the above-described configurations will be described. FIG. 6 is a circuit diagram of the mirror detection circuit 200a shown in FIG.
FIG. 6 is a waveform diagram for explaining the operation of FIG. The vertical axis in the figure indicates the signal level, and the horizontal axis indicates time. FIG. 6A shows an example of the waveform of the RF signal Srf. FIG. 6b shows the RF of FIG.
7 shows waveform examples of a top envelope signal Ste, a bottom hold signal Sbh, a bottom envelope signal Sbe in which the signal Srf is peak-held by the peak hold circuits 102 to 104, and the above-mentioned mirror detection threshold signal Smt. FIG. 6C shows a waveform example of the mirror detection signal Sm output from the comparator 109.

The RF signal Srf output from the photodetector is
As shown in FIG. 6A, the amplitude of the signal differs between the case where the light spot is on the track and the case where the light spot is on the mirror portion between the tracks. If the light spot is on the track, the RF signal Srf as shown at the peak position P4 in FIG.
Becomes large. This is because the difference in reflected light intensity between the case where the light spot is on the pit and the case where the light spot is outside the pit is large. In addition, when the light spot is directly above the pit, the reflected light intensity becomes the minimum level of the RF signal Srf, and in this case, the bottom level of the RF signal Srf becomes the lowest. Conversely, when the light spot is located at the mirror portion between the tracks, the amplitude of the RF signal Srf is small and the bottom level is high, as shown at the peak position P3 in FIG. 6A. This is because there is no pit in the mirror portion and the intensity of reflected light increases. However,
In an ordinary optical disc reproducing apparatus, even when the light spot is located at the center of the mirror section, a part of the light spot overlaps an adjacent track, and the intensity of the reflected light is modulated at the overlapping portion. Peak position P3
, A high-frequency modulation component remains in the RF signal Srf.

As shown in FIG. 6B, the top envelope signal Ste has a waveform corresponding to the top level envelope of the RF signal Srf, and the bottom envelope signal Sbe
Has a waveform corresponding to the bottom-level envelope of the RF signal Srf. Also, the bottom hold signal Sbh
Has a waveform in which the bottom level of the RF signal Srf is held. The mirror detection threshold signal Smt is a signal in which the top envelope signal Ste and the bottom hold signal Sbh are divided by the voltage dividing circuit 106 and given a predetermined offset by the offset circuit 107, and the top envelope signal Ste and the bottom It has a certain level of signal level with the hold signal Sbh. In the example of FIG. 6B, the bottom envelope signal Sbe has a signal level that is substantially intermediate between peaks and valleys. The mirror detection signal Sm is a signal obtained by comparing the bottom envelope signal Sbe and the mirror detection threshold signal Smt in the comparator 109,
In the example of FIG. 6C, when the signal level of the bottom envelope signal Sbe exceeds the mirror detection threshold signal Smt, it is at a high level (logical value '1'), and when it is below, it is at a low level (logical value '0'). .

When the light spot passes through an area on the optical disk where the intensity of reflected light is reduced due to dirt such as fingerprints, the entire amplitude of the RF signal Srf decreases as shown in a period T1 in FIG. 6A. At this time, since the amplitudes of the top envelope signal Ste and the bottom envelope signal Sbe are relatively small at the same rate, the mirror detection threshold signal S
The signal level of mt also decreases at a similar rate. That is,
Even when the amplitude of the bottom envelope signal Sbe decreases due to the decrease in the intensity of the reflected light due to dirt, the level of the mirror detection threshold signal Smt decreases at the same rate as the decrease in the amplitude, and the mirror detection becomes possible. A decrease in the mirror detection sensitivity for surface contamination is suppressed.

FIG. 7 shows a defect detection circuit 200b shown in FIG.
FIG. 6 is a waveform diagram for explaining the operation of FIG. The vertical axis in the figure indicates the signal level, and the horizontal axis indicates time. FIG. 7A shows a waveform example of the RF signal Srf. FIG. 7b shows the RF of FIG.
7 shows waveform examples of a top hold signal Sth, a top envelope signal Ste and a bottom hold signal Sbh in which the signal Srf is peak-held by the peak hold circuits 101 to 103, and the above-described defect detection threshold signal Sdt. FIG. 7C shows the converter 10
8 shows an example of the waveform of the defect detection signal Sd output from FIG.

In the period T2 in FIG. 7A, since the light spot passes through the area on the optical disk where the intensity of the reflected light is remarkably reduced due to the attachment of a scratch or dust, the RF signal S
The overall amplitude of rf is smaller. As shown in FIG. 7B, the top hold signal Sth and the bottom hold signal Sbh
Since the droop rate of the peak hold circuit 101 and the peak hold circuit 103 is slow, the signal level is maintained at a substantially constant level even in the period T2. Therefore, the signal level of the defect detection threshold signal Sdt obtained by dividing these signals at a predetermined ratio by the voltage dividing circuit 105 is also
It is constant during the period T2. When the signal level of the top envelope signal Ste, which decreases due to the decrease in the intensity of the reflected light, falls below the fixed defect detection threshold signal Sdt, the defect detection signal Sd goes high (logical value '1') as shown in FIG. 7c. Thus, a defect of the optical disk is detected.

The track pitch of a DVD is 0.74 μm, which is less than half that of a CD of 1.6 μm. On the other hand, the wavelength of the laser beam used for reproducing the DVD is 650 nm, and the wavelength of the CD is 78 nm.
Since it is only about 20% shorter than 0 nm, the ratio of the light spot diameter to the track pitch is CD
DVD is larger than DVD. And DVD
Is 0.3 μm, and 0.5 μm in CD
Since the width is larger than half of m, the ratio of the width of the mirror portion to the track pitch is smaller in DVD than in CD. That is, in the case of DVD, even when the light spot is at the center of the mirror section, the intensity of the reflected light modulated by the pitch of the adjacent track increases compared to that of the CD, so that the amplitude of the RF signal Srf increases, and The difference between the bottom level and the track portion is reduced. That is, the amplitude of the bottom envelope signal Sbe decreases.

FIG. 8A shows a waveform example of the RF signal Srf of the CD, and FIG. 8B shows a waveform example of the RF signal Srf of the DVD. As shown in these figures, the difference in bottom level between the case where the light spot is at the center of the track (on-track) and the case where the light spot is at the center of the mirror portion (off-track) is smaller for DVD than for CD. Therefore, a sufficient level difference for causing the comparator 109 to perform the comparison operation may not be obtained. For example, when the entire amplitude of the RF signal Srf decreases as shown in a period T1 in FIG.
In the case of VD, the sensitivity of the mirror detection is remarkably deteriorated, and normal track skipping reproduction may not be performed.
That is, in the mirror detection circuit 200a shown in FIG.
Since the mirror detection sensitivity is deteriorated in an optical disk such as a VD having a narrow track pitch, there is a problem that a detection failure of a mirror portion is likely to occur due to noise, contamination of the disk, or the like.

Here, the mirror detection circuit 2 of FIG.
A description will be given of another conventional mirror detection circuit which has solved the problem of 00a. FIG. 9 is a schematic block diagram showing another configuration example of the conventional mirror detection circuit. 9 includes a low-pass filter 109, a gain control amplifier 110, a gain control amplifier 112, a capacitor 111, a peak hold circuit 113, a peak hold circuit 114, a voltage divider circuit 115, an offset circuit 116, and a comparator 117. .

The low-pass filter 109 receives the input RF signal.
A high-frequency modulation component included in the signal Srf is removed, and a signal component that fluctuates according to the track and the mirror portion when the light spot crosses the track is extracted to obtain a gain control amplifier 11.
Output to 0. Gain control amplifier 110 amplifies signal S10 output from low-pass filter 109 with a predetermined gain, and outputs the amplified signal to capacitor 111. The gain of the gain control amplifier 110 is set in accordance with the type of the optical disc determined by an optical disc type determining circuit (not shown).

The capacitor 111 is connected to the gain control amplifier 11
A gain control amplifier 11 that cuts a DC component of a signal output from 0 and outputs an AC component to a gain control amplifier 112
2 amplifies, with a predetermined gain, the output signal of the gain control amplifier 110 from which the DC component has been cut;
7. Output to the peak hold circuit 113 and the peak hold circuit 114. The gain of the gain control amplifier 112 is set according to the type of the optical disk determined by the above-described optical disk type determining circuit.

The peak hold circuit 113 holds the top level of the signal S11 output from the gain control amplifier 112 at a predetermined droop rate, and outputs it to the voltage dividing circuit 115. The peak hold circuit 114 is connected to the gain control amplifier 11
The bottom level of the signal S11 output from 2 is held at a predetermined droop rate and output to the voltage dividing circuit 115. The voltage dividing circuit 115 divides the top-level signal S12 of the signal S11 held by the peak hold circuit 113 and the bottom-level signal S13 of the signal S11 held by the peak hold circuit 114 at a predetermined ratio. The divided signal is output to the offset circuit 116. Offset circuit 116
The comparator 11 outputs a mirror detection threshold signal S14 obtained by giving a predetermined offset to the divided voltage signal from the voltage dividing circuit 115.
7 is output.

The comparator 117 is connected to the gain control amplifier 1
12 is compared with the mirror detection threshold signal S14 from the offset circuit. If the output signal S11 exceeds the mirror detection threshold signal S14, a high-level mirror detection signal Sm is output. A low level mirror detection signal Sm is output.

Next, the operation of the mirror detection circuit 300 having the above-described configuration and shown in FIG. 9 will be described. FIG. 10 is a waveform diagram for explaining the operation of the mirror detection circuit 300 shown in FIG. The vertical axis in the figure indicates the signal level, and the horizontal axis indicates time.

FIG. 10A shows an example of the waveform of the RF signal Srf input to the low-pass filter 109, and FIG.
Shows the waveform of the signal S10 from which the high-frequency modulation component contained in the RF signal Srf has been removed by the low-pass filter 109. After the signal S10 is amplified by the gain control amplifier 110, the DC component is cut off by the capacitor 111 and input to the gain control amplifier 112.

FIG. 10C shows a signal S1 in which the top level of the signal S11 output from the gain control amplifier 112 is held.
2, the waveform of the signal S13 in which the bottom level is held, and the mirror detection threshold signal S14 in which the top level signal S12 and the bottom level signal S13 are divided by the voltage dividing circuit. As shown in FIG. 10D, the mirror detection signal Sm
Becomes high when the level of the signal S11 exceeds the level of the mirror detection threshold signal S14, and goes low when the level of the signal S11 falls below.

In the mirror detection circuit 300 shown in FIG.
Amplitude fluctuation according to the track and mirror portion included in the F signal Srf can be amplified to an appropriate level by the gain control amplifier 110 and the gain control amplifier 112, and the level difference of the signal input to the final stage comparator is increased. can do. Thereby, the sensitivity of the mirror detection can be improved as compared with the mirror detection circuit 200a shown in FIG.

However, the mirror detection circuit 300 shown in FIG. 9 has the following problems. FIG.
FIG. 7 is a waveform diagram for explaining a problem of the mirror detection circuit 300 shown in FIG. FIG. 11A is a diagram illustrating an example of a waveform of an input RF signal Srf. A vibration component other than an amplitude component corresponding to a track and a mirror portion at the bottom level is represented by:
It appears at the top level of the RF signal Srf. As in this waveform example, if the top level vibrates at a frequency component close to the bottom level vibration component, the low-pass filter 109
Is a signal in which a top-level signal component unnecessary for mirror detection is superimposed on a bottom-level vibration component. As a result, there is a problem that the detection failure of the mirror portion easily occurs.

FIG. 11B shows the waveforms of the output signal S11, the top hold signal S12, the bottom hold signal S13, and the mirror detection threshold signal S14 of the gain control amplifier 112 when a single jump operation is performed for only one track. Is shown. As shown in FIG. 11B, when a single jump operation is performed, the signal level held in the peak hold circuit 113 and the peak hold circuit 114 is still at the bottom level at the initial stage, and therefore, the mirror detection threshold signal S14 is Time t before rising to steady state
1, the level of the signal S11 exceeds the mirror detection threshold signal S14, and as shown in FIG.
m is rising to a high level. On the other hand, when the jumping operation over a plurality of tracks is performed, the mirror detection threshold signal S14 rising to the steady state is output to the signal S14.
At time t2 when 11 exceeds, the mirror detection signal Sm 'rises as shown in FIG. 11d. For this reason, there is a problem that the mirror detection signal Sm rises faster when a single jump operation is performed than when a jump operation over a plurality of tracks is performed. Since the mirror detection signal Sm is used not only for counting the number of tracks but also for controlling the movement of the optical pickup on the target track by applying a brake, the detection error of the mirror detection signal Sm is reduced. This may affect the brake control and cause a problem that the optical pickup cannot be stopped at a target track.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a mirror detection signal generation circuit capable of stably detecting a mirror section regardless of the type of an optical recording medium. .

[0030]

To achieve the above object, a mirror detection signal generation circuit according to the present invention is a mirror detection signal generation circuit for generating a mirror detection signal from an RF signal corresponding to light reflected from a medium. A first peak holding circuit for holding the bottom level of the RF signal at a first decay rate and outputting a bottom hold signal; and a first peak holding circuit for holding the top level of the RF signal at a second decay rate. A second peak holding circuit that outputs an envelope signal of the RF signal, a third peak holding circuit that holds a bottom level of the RF signal at a third decay rate, and outputs a second envelope signal, and the bottom holding signal. A first reference signal generating circuit that outputs a first reference signal generated based on the first reference signal and the first envelope signal; and comparing the first reference signal with the second envelope signal. And a first comparator circuit for generating a mirror detection signal.

Preferably, the first reference signal generating circuit has a first voltage dividing circuit for generating a divided voltage between the bottom holding signal and the first envelope signal. Further, the first reference signal generation circuit has a first amplifier for amplifying the divided voltage at an amplification factor according to a type of a medium. Further, the first reference signal generation circuit has an offset circuit for applying a predetermined offset voltage to the output signal of the first amplifier.

The mirror detection signal generation circuit according to the present invention further includes a filter for performing predetermined signal processing on the second envelope signal, and an amplifier for amplifying the second envelope signal at an amplification factor corresponding to the type of medium. And a second amplifier. Further, the mirror detection signal generation circuit of the present invention includes a fourth peak holding circuit for holding the top level of the RF signal at a fourth decay rate and outputting a top holding signal, the top holding signal and the bottom holding signal. A second reference signal generation circuit that outputs a second reference signal generated based on the first signal and a second reference signal that generates a defect detection signal by comparing the second reference signal with the first envelope signal. And a comparison circuit.

Preferably, the second reference signal generating circuit has a second voltage dividing circuit for generating a divided voltage of the top holding signal and the bottom holding signal. Further, the second reference signal generating circuit has a third amplifier for amplifying the divided voltage output from the second voltage dividing circuit at an amplification factor according to the type of the medium. Further preferably, there is provided a fourth amplifier for amplifying the first envelope signal at an amplification factor according to the type of the medium.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic block diagram of an optical disk reproducing device according to an embodiment of the present invention. The optical disk reproducing device 10 shown in FIG. 1 includes a disk motor 2, a head unit 3, an RF signal processing unit 4, a reproducing unit 5, a servo control unit 6, and a system control unit 7.

The disk motor 2 is used for loading a CD or D
The optical disk 1 such as a VD is held, and the optical disk 1 is rotated at a rotation speed according to the control from the servo control unit 6.
The head unit 3 includes a laser light oscillator that irradiates various optical disks 1, an optical system that irradiates and receives laser light,
A photodetector that detects light received by the optical system and converts the light into an electric signal, an RF signal amplifier that amplifies a signal from the photodetector,
A circuit for generating a focus error signal and a tracking error signal from the amplified RF signal and outputting the generated signal to the servo control unit 6 is provided. As a result, the optical disk 1 is irradiated with the laser beam, the reflected light is received, and the RF of the received light is reflected.
It performs signal conversion, amplification of the converted RF signal, and generation of a signal used for servo control such as a focus error signal and a tracking error signal from the amplified RF signal. In addition, an actuator for moving the optical system in the irradiation direction of the laser beam or in the radial direction of the disk in accordance with a control signal from the servo control unit 6 is provided.
A desired position on the optical disk 1 is irradiated with laser light, and the reflected light is received.

The RF signal processing unit 4 converts a waveform of the RF signal input from the head unit 3 into a binarized signal which is shaped and reproduces a clock signal synchronized with the binarized signal, a mirror detection circuit, and a disk defect. It has a detection circuit and the like. Thus, conversion of the RF signal into binary data, detection of a mirror portion or a defect of the optical disc 1, and the like are performed.

The reproducing unit 5 is provided with the RF signal processing unit 4
It is a block that processes the digitized digital signal to reproduce desired information. For example, in the case of a DVD player,
Demodulates the binary data modulated by the 8-16 method,
An error correction process is performed on the data stream to reproduce the data stream, and further, audio and video are reproduced from audio data and image data separated from the data stream.

The servo control unit 6 controls the rotation speed of the disk and the irradiation position of the laser beam by controlling the actuator of the disk motor 2 and the head unit 3. For example, the rotation speed of the disk is servo-controlled according to the position of the head unit 3 in the disk radial direction, and the data reading speed on the inner and outer peripheral sides of the disk is controlled to be constant. When an instruction to skip a track is input from the system control unit 7, the head unit 3 is moved in the radial direction of the disk, and the spot of the laser beam is moved to a desired track. In addition, the actuator of the head unit 3 is servo-controlled in accordance with the focus error signal and the tracking error signal input from the head unit 3 to correct the deviation of the laser beam focus and the track scanning, and to read the recording data stably. Hold ready to be put out.

The system control unit 7 discriminates the type of the disc to be inserted, controls the mirror signal detection and defect detection in the RF signal processing unit 4, controls the binarized data reproduction process in the reproduction unit 5, the servo control unit 6. And various controls relating to the entire system, such as the control of the drive of the disk motor 2 and the head unit 3.

The operation of the optical disk reproducing apparatus having the above configuration will be described. When a new optical disk 1 is loaded, the type of the optical disk 1 is determined before the recorded data is reproduced. First, the instruction to scan the focus is sent from the system control unit 7 to the servo control unit 6.
To thereby scan the focus position of the head unit 3 in the direction perpendicular to the recording surface. The RF signal at this time is R
A small change in the amplitude of the RF signal that is input to the F signal processing unit 4 is detected and output to the system control unit 7. The system controller 7 determines the type of the optical disc 1 from the focus position at the time when the amplitude fluctuation of the RF signal is detected. This is a discrimination method utilizing the fact that the depth from the transparent resin layer on the optical disk surface to the recording layer is different in optical disks such as CDs and DVDs. The above-described disc discrimination method is merely an example, and various other discrimination methods according to the specifications of the optical disc can be applied. For example, when the type can be determined by the shape of the disk, a sensor for detecting the shape may be separately provided.

When the type of the optical disk 1 is determined by the system control unit 7, the signal detection gain, detection threshold value, filter frequency characteristics, and the like are determined in the mirror detection unit and the defect detection unit of the RF signal processing unit 4. It is set according to the type. The details will be described later.

At the time of reading the recorded data from the optical disk 1, settings such as the rotation speed of the disk, the position of the laser light spot, and the focus of the laser light are output from the system control unit 7 to the servo control unit 6. The disk motor 2 and the actuator of the head unit 3 are servo-controlled using the focus error signal and the tracking error signal of the head unit 3 as feedback signals. Thus, the spot of the laser beam is stably scanned on the track of the optical disc 1. The reflected light of the laser beam received by the optical system of the head unit 3 is converted to an RF signal by a photodetector circuit, further amplified by an RF signal amplifier, and output to the RF signal processing unit 4. The RF signal is binarized by the waveform shaping in the RF signal processing unit 4 and reproduced into desired information in the reproduction unit 5.

During the track jump operation, the head unit 3
The actuator is controlled by the servo control unit 6 so that the slider slides in the radial direction of the disk toward the jump destination track. At this time, the number of pulses of the mirror detection signal output from the mirror detection circuit of the RF signal processing unit 4 is counted by the system control unit 7, and the number of skipped tracks is grasped. If it is determined from the counting result that the light spot has reached the target track, the slide movement of the head unit 3 is brake-controlled so that the light spot is applied to the center of the target track. The position of the part 3 is controlled.

Next, the mirror detection circuit and the defect detection circuit included in the RF signal processing section 4 will be described. FIG. 2 is a schematic block diagram of a mirror detection circuit and a defect detection circuit according to the embodiment of the present invention. The mirror detection circuit 100a shown in FIG.
2 to a peak hold circuit 14, a voltage dividing circuit 16, a low-pass filter 21, a gain control amplifier 19 and a gain control amplifier 20, an offset circuit 22 and a comparator 24. The defect detection circuit 100b shown in FIG. 2 includes a peak hold circuit 11, a voltage divider circuit 15, a gain control amplifier 17, a gain control amplifier 18, and a comparator 23, and detects the peak hold circuit 12 and the peak hold circuit 13 by mirror detection. It is shared with the circuit 100a.

The peak hold circuits 11 to 14 are circuits for holding the top level or the bottom level of the RF signal Srf converted into an electric signal in the photodetector of the head unit 3. The peak hold circuit 11 and the peak hold circuit 12 hold the top level of the RF signal Srf, and the peak hold circuits 13 and 14 hold the bottom level of the RF signal Srf.

The droop rate of each peak hold circuit is set individually for each peak hold circuit, and the nature of the signal held in each peak hold circuit differs depending on the value of the droop rate. In the peak hold circuit 11, a relatively slow droop rate is set in order to keep the top level of the RF signal Srf constant, for example, a droop rate of about 1 [msec / V] is set. Further, it outputs the generated top hold signal Sth to the voltage dividing circuit 15. The peak hold circuit 12
In order to output a signal corresponding to the envelope drawn by the top level of the signal Srf, a droop rate faster than the peak hold circuit 11 is set, for example, 100 [usec /
[V]. Further, the generated top envelope signal Ste is output to the voltage dividing circuit 16 and the gain control amplifier 18. Peak hold circuit 1
In No. 3, a relatively slow droop rate is set to keep the bottom level of the RF signal Srf constant, for example, a droop rate of about 10 [msec / V] slower than that of the peak hold circuit 11 is set. . Further, it outputs the generated bottom hold signal Sbh to the voltage dividing circuit 16. In the peak hold circuit 14, a droop rate faster than that of the peak hold circuit 12 or the peak hold circuit 13 is set in order to output a signal corresponding to an envelope drawn by the bottom level of the RF signal Srf, for example, 10 [usec / V]. ]
Dru plate of the degree is set. Further, the generated bottom envelope signal Sbe is
Output to

The peak hold circuit 13 changes the droop rate according to the droop rate setting signal Sc5 from the system control unit 7. The speed of this droop plate is higher than that of a normal state when a defect of the optical disk described later is detected, thereby speeding up the response of the hold signal to a sudden change in the bottom level. Also, the droop rate of other peak hold circuits may be changed under the control of the system control unit 7. Thereby, for example, an appropriate droop rate according to various conditions such as the determined type of the optical disc 1 and the reproduction speed can be set in each peak hold circuit.

The low-pass filter 21 is a filter for removing high-frequency noise components contained in the bottom envelope signal Sbe output from the peak hold circuit 14.
Further, under the control of the system control unit 7, the frequency band may be changed according to the reproduction conditions such as the type of the optical disc 1 and the reproduction speed. This makes it possible to appropriately set a trade-off relationship between the removal of the noise component and the response speed of the envelope signal.

The voltage dividing circuit 15 includes the peak hold circuit 11
A signal obtained by dividing the top hold signal Sth output from the PDP and the bottom hold signal Sbh output from the peak hold circuit 13 at a predetermined ratio is output to the gain control amplifier 17. Further, the voltage division ratio changes according to the voltage division ratio setting signal Sc6 from the system control unit 7. This partial pressure ratio is set for each type of the determined optical disc 1. Voltage dividing circuit 16
Outputs to the gain control amplifier 19 a signal obtained by dividing the top envelope signal Ste output from the peak hold circuit 12 and the bottom hold signal Sbh output from the peak hold circuit 13 at a predetermined ratio. Further, the voltage division ratio changes according to the voltage division ratio setting signal Sc7 from the system control unit 7. This partial pressure ratio is set for each type of the determined optical disc 1.

The gain control amplifier 17 amplifies the divided signal S1 output from the voltage dividing circuit 15 with a gain corresponding to the gain setting signal Sc1 from the system control unit 7, and uses the amplified signal as a defect detection threshold signal Sdt. The signal is input to the positive terminal of the comparator 23. The gain control amplifier 18 amplifies the top envelope signal Ste output from the peak hold circuit 12 with a gain according to the gain setting signal Sc2 from the system control unit 7, and inputs the amplified signal to the negative terminal of the comparator 23. The gain control amplifier 19 converts the divided voltage signal S2 output from the voltage dividing circuit 16 into a gain setting signal Sc3 from the system control unit 7.
, And input to the offset circuit 22. The gain control amplifier 20 amplifies the bottom-level envelope signal S3 output from the low-pass filter 21 with a gain corresponding to the gain control signal Sc4 from the system control unit 7, and outputs the amplified signal to the positive terminal of the comparator 24.

In a normal case, the gain control amplifier 19 and the gain control amplifier 20 are set to the same gain, and the gain control amplifier 17 and the gain control amplifier 18 are also set to the same gain. Different values may be set as appropriate.

The offset circuit 22 is connected to the gain control amplifier 1
A predetermined offset is added to the divided signal output from the comparator 9 and the resulting offset is input to the negative terminal of the comparator 24 as a mirror detection threshold signal Smt.

Comparator 23 and Comparator 24
Compares the signal level input to the positive terminal with the signal level input to the negative terminal. If the signal level of the positive terminal is higher than that of the negative terminal, It outputs a signal, and outputs a logical value “0” when it is smaller.
When the level of the top envelope signal S5 amplified by the gain control amplifier 18 becomes smaller than the defect detection threshold signal Sdt, the comparator 23 outputs a defect detection signal Sd of a logical value '1' for notifying the detection of the defect. I do. When the level of the bottom-level envelope signal S4 amplified by the gain control amplifier 20 is higher than the mirror detection threshold signal Smt, the comparator 24 outputs the mirror detection signal Sm of logical value "1" indicating the detection of the mirror portion. Output.

The mirror detection circuit 10 having the above configuration
0a and the operation of the defect detection circuit 100b will be described. In the mirror detection circuit 100a, the top envelope signal Ste and the bottom hold signal Sbh of the RF signal Srf are divided in the voltage dividing circuit 16, and a divided signal S2 having a signal level of a predetermined ratio between these signals is generated. .
The divided signal S2 is amplified by a gain according to the type of the optical disc 1 in the gain control amplifier 19, and then added with a predetermined offset in the offset circuit 22, and is supplied as a mirror detection threshold signal Smt to the negative terminal of the comparator 24. Is input to On the other hand, the bottom envelope signal Sbe of the RF signal Srf is filtered by a low-pass filter 21 to remove high-frequency noise components, and is amplified by a gain control amplifier 20 with a gain corresponding to the type of the optical disc 1. Is input to If the level of the amplified bottom envelope signal S4 exceeds the mirror detection threshold signal Smt, the comparator 24 outputs a mirror detection signal Sm having a logical value of "1" indicating the detection of the mirror section.

In the defect detection circuit 100b, the RF signal Srf
The top hold signal Sth and the bottom hold signal Sbh are divided by the voltage dividing circuit 15 to generate a divided signal S1 having a signal ratio of a predetermined ratio between these signals. The divided signal S1 is amplified by the gain control amplifier 17 with a gain corresponding to the type of the optical disc 1, and is then input to the positive terminal of the comparator 23 as a defect detection threshold signal Sdt. On the other hand, the top envelope signal Ste of the RF signal Srf is amplified by the gain control amplifier 18 with a gain corresponding to the type of the optical disc 1, and then input to the negative terminal of the comparator 23. When the amplified top envelope signal S5 falls below the defect detection threshold signal Sdt, a logical value indicating that a defect has been detected on the optical disc 1
The comparator 23 outputs the defect detection signal Sd of 1 '.

When the light spot passes through an area on the optical disk where the reflected light intensity is reduced due to dirt such as fingerprints, the entire amplitude of the RF signal Srf is reduced. At this time, the top envelope signal Ste and the bottom envelope signal Since the amplitude of Sbe decreases relatively at the same rate, the signal level of the mirror detection threshold signal Smt also decreases at the same rate. That is, even when the amplitude of the bottom-level envelope signal decreases due to a decrease in the intensity of the reflected light due to dirt, the level of the mirror detection threshold signal Smt decreases at the same rate as the decrease in the amplitude, thereby enabling the mirror detection. As a result, a decrease in the mirror detection sensitivity with respect to the contamination of the disk surface is suppressed, and stable mirror detection becomes possible.
Similarly, in the defect detection circuit 100b, when the entire amplitude of the RF signal Srf decreases due to contamination of the disk surface or the like, the level of the top hold signal Sth and the level of the top envelope signal Ste are relatively proportionally changed accordingly. Since the size becomes smaller, the variation of the relative threshold level at which a defect is detected is suppressed, and stable defect detection becomes possible.

Furthermore, since the divided voltage signal S2 and the bottom envelope signal S3 are amplified with a gain corresponding to the type of the optical disc 1, the jump is performed on an optical disc such as a DVD for a CD in which the level of the bottom envelope signal S3 is relatively small. Also in the case where the reproduction is performed, the gain of the gain control amplifier 19 and the gain control amplifier 20 can be set large to suppress the decrease in the signal level difference input to the comparator 24. It is suppressed and stable mirror detection becomes possible. Similarly, also in the defect detection circuit 100b, the divided voltage signal S1 and the top envelope signal Ste are amplified with a gain corresponding to the type of the optical disk 1, so that, for example, the amplitude of the RF signal Srf is relatively stable even on an optical disk. Defect detection becomes possible.

When the defect detection signal Sd becomes the logical value "1" in the defect detection circuit 100b, the droop rate of the peak hold circuit 13 is increased by the system control unit 7 which has detected the defect detection signal Sd from the normal value. The droop rate setting signal Sc5 to be output is output. With this droop rate setting signal Sc5, the defect detection signal Sd becomes a logical value
The speed of the droop rate of the peak hold circuit 13 is increased during the period of 1 '.

FIG. 3 is a waveform diagram showing a bottom hold signal Sbh at a defective portion of the optical disk. The vertical axis in the figure indicates the signal level, and the horizontal axis indicates time. FIG. 3A shows the waveforms of the RF signal Srf and the divided voltage signal S1 when the light spot passes through the defective area of the optical disk, and FIG. 3B changes from the logical value '0' to the logical value '1' according to the defect. The waveform of the defect detection signal Sd is shown. FIG. 3c also shows
Compare the waveform of the bottom hold signal Sbh, the divided voltage signal S2 and the bottom envelope signal S3 when the droop rate of the peak hold circuit 13 is accelerated with the waveform of the bottom hold signal Sbh 'when the droop rate is not accelerated. It is shown. As shown in FIG. 3A, when the intensity of the reflected light is significantly reduced due to a defect or a deposit on the optical disk and the top level of the RF signal Srf is lower than the bottom level in the normal state, the normal state is maintained. Bottom hold signal S held by slow droop rate
As shown in FIG. 3c, bh 'maintains the level at the time of defect detection even after defect detection. For this reason, the level of the mirror detection threshold signal Smt remains low, and normal mirror detection cannot be performed. On the other hand, in the mirror detection circuit 100a shown in FIG. 2, when the defect detection signal Sd becomes a logical value "1", the droop rate of the peak hold circuit 13 is increased, and as shown in FIG. The threshold signal Smt is a logical value of the defect detection signal Sd.
After returning to 0 ', it returns to the normal level immediately.
Therefore, the inoperable state of the mirror detection after the defect detection can be minimized.

The mirror detection circuit 100a shown in FIG.
In the above, since a low-pass filter 21 removes a noise component unnecessary for mirror detection included in the bottom envelope signal Sbe, for example, a noise component generated when tracks on which the same data is continuously recorded for a long time are adjacent to each other. Can remove glitches in the mirror detection signal Sm.

FIG. 4 is a waveform diagram showing noise of the RF signal Srf generated when the light spot traverses an adjacent track where values “1” or “0” are continuous. For example, when a pit portion is continuous on an adjacent track, a glitch in the bottom level direction occurs as shown at the peak position P1 of the bottom envelope due to a decrease in reflected light due to the pit portion. Further, when a portion having no pits on an adjacent track, that is, a mirror portion is continuous, a glitch in the top level direction as shown by the peak position P2 of the bottom envelope occurs due to an increase in reflected light by the mirror portion. I do. In the mirror detection circuit 100a shown in FIG. 2, such a noise component is effectively removed by the low-pass filter 21, so that stable mirror detection is possible.

As described above, according to the mirror detection circuit 100a shown in FIG. 2, in the peak hold circuit 13, the bottom level of the RF signal Srf is held by the first droop plate, and the bottom hold signal Sbh is output. You. In the peak hold circuit 12, the RF signal Srf
Top level faster than first drue plate second
, And a top envelope signal Ste is output. In the peak hold circuit 14, the bottom level of the RF signal Srf is held at the third droop rate faster than the second droop rate, and the bottom envelope signal Sbe is output. In the voltage dividing circuit 16, the bottom hold signal Sbh and the top envelope signal Ste are divided at a predetermined ratio, and a divided signal S2 is output. In the gain control amplifier 19, the divided signal S2
Is the gain setting signal S input from the system controller 7.
The signal is amplified by the first gain according to c3. In the gain control amplifier 20, the bottom envelope signal Sbe is amplified with a second gain according to the gain setting signal Sc4 input from the system control unit 7. The mirror detection threshold signal Smt having the divided voltage signal S2 amplified by the gain control amplifier 19 and having an offset added thereto is compared with the bottom envelope signal S4 amplified by the gain control amplifier 20 by the comparator 24. A corresponding mirror detection signal Sm is output. Accordingly, in a track jump operation of an optical disc such as a DVD for a CD, in which an RF signal level difference between an on-track and an off-track is relatively small, a malfunction in mirror detection due to noise or the like is suppressed. Thereby, in the optical disc reproducing apparatus shown in FIG. 1, the stability of the track skipping operation in the skipping reproduction, the search, and the like is improved.

The low-pass filter 21 for removing noise components contained in the bottom envelope signal Sbe detects mirrors such as noise as shown in FIG. 4 and noise due to high-frequency signal components modulated by pit reflection. Since unnecessary noise components are removed, malfunctions in mirror detection are suppressed, and the stability of the track jumping operation in skipping reproduction, search, and the like is improved.

In the peak hold circuit 11,
The top level of the RF signal Srf is held at a fourth droop rate faster than the first droop rate and slower than the second droop rate, and the top hold signal Sth is output. In the voltage dividing circuit 15, the bottom hold signal Sbh and the top hold signal Sth are divided at a predetermined ratio, and a divided signal S1 is output. The amplified signal of the divided signal S1 and the amplified signal of the top envelope signal Ste are compared in the comparator 23, and a defect detection signal Sd according to the comparison result is output. According to the defect detection signal Sd, the droop rate of the peak hold circuit 13 is set to the first level.
Is changed to a predetermined droop rate faster than the droop rate. Therefore, it is possible to prevent the bottom hold signal Sbh after the defect detection on the optical disk due to a scratch or an adhering substance from being held at the level at the time of the defect detection, and to minimize the defect period of the mirror detection operation after the defect detection. Can be suppressed.

As in the conventional mirror detection circuit 300 shown in FIG. 9, a failure does not occur in the mirror detection operation due to the vibration component generated at the top level, so that the mirror detection operation is more stable than the conventional circuit in FIG. Becomes possible. Further, the mirror detection threshold signal Smt does not fluctuate transiently during the single jump operation of only the track,
Since there is no difference from the steady level in the jump operation of a plurality of tracks, no error occurs in the mirror detection signal Sm at the time of the single track jump operation as in the mirror detection circuit 300 of FIG. Thereby, for example, the brake control of the head unit 3 using the mirror detection signal Sm can be stably performed. In the present invention, since the amplifiers are provided between the peak hold circuits 11, 12, 13, and 14 and the input terminals of the comparators 23 and 24 to amplify each signal, the defect detection signal and the mirror detection signal are output. It can be detected stably. Peak hold circuits 11, 12, 13,
In the case where an amplifier is provided before the stage 14, it is necessary to increase the dynamic range, but this is not necessary by adopting the configuration as in the present invention.

The present invention is not limited to the above embodiment. For example, the defect detection circuit for switching the droop rate of the peak hold circuit 13 to a high rate is not limited to the configuration shown in FIG. 2, but may have other various configurations. Further, the droop rate of the peak hold circuit 11 to the peak hold circuit 14, the voltage division ratio of the voltage divider circuits 15 and 16, the gains of the gain control amplifiers 17 to 20, the band characteristics of the low-pass filter 21, the offset circuit 22 , And the offset and hysteresis characteristics of the comparator 23 and the comparator 24 are all controlled by the system control unit 7.
For example, the configuration may be variable depending on the type of the optical disk, or any one of them may be set as a fixed value.

[0067]

According to the mirror detection signal generation circuit of the present invention, the mirror section can be detected stably regardless of the type of the optical recording medium, and the jumping operation of one track can be performed stably.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of an optical disk reproducing device according to an embodiment of the present invention.

FIG. 2 is a schematic block diagram of a mirror detection circuit and a defect detection circuit according to the embodiment of the present invention.

FIG. 3 is a waveform diagram showing a bottom hold signal in a defective portion of the optical disc.

FIG. 4 is a waveform diagram illustrating noise of an RF signal generated when a light spot crosses an adjacent track where values “1” or “0” are continuous.

FIG. 5 is a schematic block diagram illustrating a configuration example of a conventional mirror detection circuit and a defect detection circuit.

FIG. 6 is a waveform chart for explaining the operation of the mirror detection circuit shown in FIG. 5;

FIG. 7 is a waveform chart for explaining the operation of the defect detection circuit shown in FIG.

FIG. 8 is a waveform chart for explaining a difference between RF signals of a CD and a DVD.

FIG. 9 is a schematic block diagram illustrating a configuration example of a conventional mirror detection circuit.

FIG. 10 is a waveform chart for explaining an operation of the mirror detection circuit shown in FIG. 9;

FIG. 11 is a waveform chart for explaining a problem of the mirror detection circuit shown in FIG. 9;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2 ... Disk motor, 3 ... Head part,
4 RF signal processing unit, 5 reproduction unit, 6 servo control unit,
7: system control unit, 11 to 14: peak hold circuit, 15, 16: voltage divider circuit, 17 to 20: gain control amplifier, 21: low-pass filter, 22: offset circuit,
23, 24 comparator, 10 optical disk reproducing device, 100a mirror detection circuit, 100b defect detection circuit

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Toshio Yamauchi 6-24-1, Nishi-Shinjuku, Shinjuku-ku, Tokyo F-term in Texas Instruments Co., Ltd. (reference) 5D117 AA02 BB01 BB02 CC06 EE14 FF01 FF14 FF15 5D118 AA17 BF12 BF13 CD03 CD06 CD09

Claims (10)

[Claims] 1. A mirror detection signal generation circuit for generating a mirror detection signal from an RF signal corresponding to light reflected from a medium, wherein a bottom level of the RF signal is held at a first attenuation rate. A first peak holding circuit that outputs a first envelope signal while holding a top level of the RF signal at a second decay rate, and a bottom level of the RF signal. A third peak holding circuit that holds the signal at a third decay rate and outputs a second envelope signal; and outputs a first reference signal generated based on the bottom holding signal and the first envelope signal. A first reference signal generation circuit; and a first comparison circuit that compares the first reference signal with the second envelope signal to generate a mirror detection signal. circuit. 2. The mirror detection signal according to claim 1, wherein the first reference signal generating circuit has a first voltage dividing circuit for generating a divided voltage between the bottom holding signal and the first envelope signal. Generation circuit. 3. The mirror detection signal generation circuit according to claim 2, wherein the first reference signal generation circuit has a first amplifier for amplifying the divided voltage at an amplification factor according to a type of a medium. 4. The first reference signal generation circuit according to claim 1, wherein
4. The mirror detection signal generation circuit according to claim 3, further comprising an offset circuit for applying a predetermined offset voltage to an output signal of the amplifier. 5. A filter for performing predetermined signal processing on the second envelope signal, and a second amplifier for amplifying the second envelope signal at an amplification factor according to a type of a medium. Item 5. The mirror detection signal generation circuit according to item 1, 2, 3, or 4. 6. A fourth peak holding circuit that holds a top level of the RF signal at a fourth decay rate and outputs a top holding signal, and is generated based on the top holding signal and the bottom holding signal. A second reference signal generation circuit that outputs a second reference signal; and a second comparison circuit that compares the second reference signal with the first envelope signal to generate a defect detection signal. The mirror detection signal generation circuit according to claim 1, 2, 3, 4, or 5. 7. The mirror detection signal generation circuit according to claim 6, wherein the second reference signal generation circuit has a second voltage division circuit for generating a divided voltage of the top hold signal and the bottom hold signal. . 8. The second reference signal generation circuit according to claim 2, wherein
8. The mirror detection signal generation circuit according to claim 7, further comprising a third amplifier that amplifies a divided voltage output from the divided voltage circuit with an amplification factor according to a type of the medium. 9. The mirror detection signal generation circuit according to claim 7, further comprising a fourth amplifier for amplifying the first envelope signal at an amplification factor according to a type of a medium. 10. The mirror detection signal generation circuit according to claim 6, wherein the first decay speed is increased when the defect detection signal is output.